Effect of Water Deficit on Grain Yield and Yield Components Ispaghula (Plantago ovata Forssk.)

Drought is the major limiting factor of plant growth and productivity in many regions of the world. to determine the response of different ecotypes of ispaghula (plantago ovata forssk.) to drought stress, a field experiment was conducted at the research institute of forests and rangelands, tehran, iran in 2018. the experimental design was a split plot based on a randomized complete block design (rcbd) with three replications. the main factor included drought stress at three levels control (d1), drought stress after flowering stage with supplemental irrigation in the filling stage (d2), and post-flowering drought stress (d3). the second factor contained eight ecotypes of plantago ovate, including dehloran (3328), alborz (3968), markazi (14592), dashtestan (21228), hormozgan-1 (31536), hormozgan-2 (31563), ghaen (37496), and sarbisheh (38917). the results showed a significant effect of drought stress and ecotypes for all traits (p<0.01). the interaction between ecotypes and drought stress was not significant for yield and yield components. ispaghula ecotypes showed similar responses to drought stress. the highest grain yield with an average value of 720 kg/ha was obtained in ecotype 3328 and it was considered as the best ecotype to cope drought stress conditions. ispaghula grain yield decreased by an average of 11.02% and 23.65% with drought stress d2 and d3 in comparison with control (d1), respectively. a significant difference between d2 and d3 were observed, so that the grain yield of d3 was 11.26% lower than d2. regardless of the drought stress level, ecotype dehloran (3328) produced the highest grain and was recommended for breeding improved varieties. considering drought the ecotype dehloran (3328) that had a good yield under normal irrigation conditions produced the least yields than other ecotypes